Expansible cloth and method of making it



Nov. 6, 1951 w. w. ROWE 2,573,773

EXPANSIBLE CLOTH AND METHOD OF MAKING IT Filed Nov. 12, 1948 44 J BYMYW ATTORNEYS- Patented Nov. 6, 1951 EXPANSIBLE CLOTH AND METHOD OF MAKING IT William Wallace Rowe, Cincinnati, Ohio, assignor to Cincinnati Industries, Inc., Cincinnati, Ohio, a corporation of Ohio Application November 12, 1948, Serial No. 59,619-

(Cl. fi l-33.05)

14 Claims. 1

This application is a continuation-in-part of my copending application entitled Method of Making Expansible Cloth, Serial No. 444,298, filed May 25, 1942, now abandoned.

My invention has to do with imparting stretchability to woven cloth by procedures analogous to creping; it has for its object the formation of a new type of expansible cloth having very many advantages, as will appear hereinafter, and a mode of making it.

By a creplng procedure I mean an operation in which a web of material to be creped is caused to adhere to a creplng surface-usually a creplng cylinder-and is removed therefrom by a creplng doctor which crowds the web back upon itself. These operations have always hitherto resulted in the production of rugosities or folds in the web, which are called creping crinkles. Such creping crinkles have been the distinguishing characteristic of webs gathered by-creping.

It has many times been suggested that woven cloth can be creped as paper is creped. It is possible, by using a suitable positive adhesive substance to cause the cloth to adhere to a creplng surface, to impart creplng crinkles to cloth much as these crinkles are imparted to paper. But cloth presents some peculiar problems. The bulk of a cloth web is usually greater than that of paper of the same or similar weight. This, together with the structure of cloth (as compared with the relatively homogeneous or amorphous nature of paper), tends to affect the character of the crinkles and to make them objectionably coarse and irregular. By the same token the effective thickness of the cloth is increased by creplng in a way which is undesirable for many uses. Cloth moreover, is not a material which will retain a crease or fold as readily as paper or other crepable webs. As a consequence, the creplng crinkles have a tendency to come out or unfold. It is sometimes possible by treating the cloth with a heavy, continuous or substantially continuous coating of substance (which may or may not be the creplng adhesive), to crepe the product and cause the stiffness of the coating to retain, or assist in retaining the crinkles. In other instances it is possible by coating the cloth with a layer of adhesive which is strongly adherent to itself, to cause the adhesive to tie acrossv the creplng crinkles formed in the cloth by the doctor, in such a way as to resist the unfolding of the crinkles. It is also possible to cement to cloth a web of paper or some other crepable film or web, and crepe the composite product, relying upon the added film or web to preserve the crep- 2 ing crinkles. because of the bulk and structure cf the material being creped, the effective thickness of the material is very greatly increased, and the crinkles are very coarse and irregular.

Since it is one of the objects of my invention to provide a resin treated expansible cloth, which will have the property of flow in the mold, in accordance with the teachings of my Patent No. 2,343,930 dated March 14, 1944, it' is one of the objects of my invention to produce a contracted cloth which will be uniform in its characteristics but which will be bulked very little. The utility of my contracted cloth is, however,-not confined to such uses, and will be found of value in all instances where a highly expansible cloth is desired, as for example, in rubberized cloth or laminated articles including rubber, or in bags or other containers where the cloth may be used either alone or in combination with stretchable paper.

The nature of woven cloth is such that it is inherently stretchable along the bias directions; but it is not appreciably stretchable in the directions in which the warp and woof threads extend, i. e., it is not stretchable in those directions beyond the inherent stretchability of the threads themselves, which of course, is relatively slight. It is an object of my invention to provide a contracted cloth which will be stretchable in all directions and irrespective of the direction of the threads.

It is an object of my invention to provide a contracted cloth which, while having a high degree of universal expansibility, is not characterized by prominent creplng crinkles or rugosities. and in many instances is not characterized by any observable rugosities or crinkles.

It is an object of my invention to provide a contracted cloth which is not necessarily associated with any thick, heavy or continuous film of adhesive substance.

These and other objects of my invention which will be set forth hereinafter or will be apparent to one skilled in the art upon reading these specifications, I accomplish in that product and by that procedure of which I shall now describe certain exemplary embodiments.

Reference is made to the drawings in which:

Figure 1 is a diagrammatic plan view of an apparatus for imparting universal stretchability to webs.

Figure 2 is a diagrammatic view showing an apparatus for applying a creplng adhesive to webs.

In all of these procedures however, I

covery that by certain procedures hereinafter taught in detail, I can crepe cloth in such a way as to impart a high degree of stretchability to it without producing marked or prominent creping crinkles therein, and in many instances without producing any observable creping crinkles. My invention is applicable to any cloths in which the weave is not absolutely tight, 1. e., to any cloths in which the threads are not crowded tightly together. I shall refer to the cloths to which my invention applies as cloths of open weave; but it is not to be understood that this implies a mesh fabric, or a material having necessarily as open a weave as scrim. n the contrary, many fabrics which would appear to the eye as having a tight weave, are in fact capable of treatment in accordance with this invention.

I have found that by the procedure hereinafter outlined, I may take open weave cloth and treat it in such a manner that the change in it to the eye appears to lie predominantly, if not entirely, in a closing u of the weave of the cloth, but in which, by reason of the contracting operations to which I submit the cloth, a high degree of stretchability has been imparted thereto without any substantial increase in the effective thickness of the cloth web, and without the production of marked or apparent creping crinkles.

In the instance of a cloth of such open weave that the interstice between the threads are very apparent to the eye, and are much broader than the threads themselves, the visual result of my process will be appreciated by comparing Figs. 3 and 4.

Figure 3 in its lower part shows at I the cloth in its original visual condition, while Fig. 4 shows at 2 the cloth in it ultimately contracted condition. It will be noted that the most obvious difference to the eye is an apparent closing up of the weave of the fabric in both directions.

The application of an adhesive to the cloth tends in normal practice to cause the adhesive to strike into the cloth. This causes the warp and woof threads to become more or less locked where they cross, and tends in large measure to cause the cloth to form into relatively large and coarse creping crinkles as it is being removed from the creping surface by the doctor. I first found that by controlling both the consistency of the creping adhesive 50 as to cause it to be non-saturating in character, and by applying it so that it exist primarily as interspaced dots or islands of adhesive located only upon the tops of the rugosities of the fabric, I could bring about a wholly different action during creping, with the fabrics noted above. This condition of the adhesive treated fabric is diagrammatically illustrated in Figure 5, where a woof thread is indicated at 3 and warp threads at 4. The adhesive exists primarily in masses or 6 located at the crests of the threads, regarding them as cor- 4 rugated members. It will be noted that the adhesive has neither penetrated the threads nor the body of the cloth, and that it does not serve to bind the threads together at the places where they cross. Nothing like a continuous film of the adhesive is formed. A further desirable characteristic of the adhesive masses 5 and 6 is that they should be strongly adherent to each other.

The characteristics of the adhesive itself may be controlled by controlling its viscosity at the time of application. With thermo-plastic adhesives thi may be done by controlling their temperatures. With adhesives which are soluble in or may be softened by a suitable solvent or vehicle, the viscosity may be regulated by the proportion of solids to solvent. Combinations of solvent and heat may likewise be employed. The adhesives may be any of a wide variety of substances, including any of the thermoplastic synthetic resins, incompletely polymerized thermosetting resins, synthetic resins of all kinds, the various bitumens, rubber, rubber latices and dispersions, waxes, and natural resins, compositions of resin and rubber, or bitumen and rubber, and various adhesives of animal or vegetable originin short, any adhesive which under working conditions may be brought to a non-saturating viscosity, while retaining adhesion to itself, and which may be applied as hereinafter set forth.

The adhesive treated cloth is also illustrated diagrammatically at l in Figure 3.

I found that when such treated cloth is caused to adhere to a creping cylinder and is removed therefrom by means of a doctor, the primary action is a crowding of the threads together. Depending upon the relationship of the creping doctor to the threads constituting the weave of the cloth, one set of threads only, or both sets of threads may be crowded together is a single gathering operation. The condition of the gathered cloth when both sets of threads are crowded together is diagrammatically illustrated at 8 in Figure 4, and also in Figure 6. In the latter figure, it will be noted how the woof thread 3 has become more corrugated. The depth of the corrugations has increased, while the pitch has diminished; and the number of corrugations per unit of length has been multiplied. Moreover, the adhesive areas of islands 5 and 6 have come together, in instances at least, and have adhered, holding the cloth in its contracted condition. The effective thickness of the cloth has not been materially increased; but very substantial stretchability has been imparted to it.

In the practice of my invention, an important part of the total stretchability of my fabrics lies in a crowded or gathered condition illustrated in Figures 4 and 6. There may at the same time be formed some creping crinkles, and my invention does not exclude the formation of these; but I have noted it as a characteristic of creping under conditions in which the cloth web is free to become contracted as shown in Figures 4 and 6, that any creping crinkles concurrently formed tend to be finer and to bulk the web less than the crinkles which would form in ordinary creping operations carried on on the same cloth.

I shall now describe a typical operation under my invention. A web of cloth 9 is withdrawn from the roll l0 and is led through a coating apparatus. In this apparatus a roll I I picks up adhesive l2 from a pan l3. In the exemplary embodiment, the adhesive is an incompletely polymerized thermo-setting resin which, in order to minimize premature polymerization, I have cut 5 back with a suitable solvent, such as alcohol, so that if warming ,ispracticed at all, no very high temperature need be used. It will be understood that the amount of solvent is small, and that the adhesive is in a highly viscous state, having little tendency to saturate or strike into an obsorbent substance.

The adhesive picked up by the roll ll may be doctored to a very thin film by the roll M. This thin film, on the surface of the roll I, is applied to the surface of the web 9, the web being pressed against the film by a backing roll l5, preferably rubber covered. Because of the control both of film thickness and of the viscosity of the coating substance, the coating substance is so imposed on the cloth as essentially to form discontinuous spots of coating on the crests or high points of the threads only. The coating does not strike through the web. The coated cloth may be rewound as at I 6 after drying.

The roll [6 may be next taken to a creping machine, or the coated fabric may be led directly to the creping machine without rewinding. In Figure 1, I have shown a machine of the general type illustrated in the Kemp Patents 2,008,181

and 2,008,182; but other kinds of creping apparatus may be employed. An advantage of the Kemp apparatus is that it successively contracts the web on oppositely disposed diagonal lines, thus imparting to it crossing sets of creping crinkles, both sets being disposed aslant to the major axis of the web.

The adhesive treated cloth may first be led over a steam table ll or like device to warm the adhesive or dry the solvent out of it, and in either event to bring it to the proper tack for creping. Then the cloth is led against the surface of the first creping cylinder IB, the adhesive being disposed against the cylinder, and the cloth will be pressed against the cylinder by a pressure roll Mia. The cloth is removed from the surface of the cylinder by a creping knife or doctor [9, disposed diagonally or aslant to the direction of the motion of the cloth. The amount of stretchability imparted by this creping operation may be controlled and varied in accordance with principles outlined in the Kemp patents.

For the second creping operation, the web is led to a second creping cylinder 20, and pressed thereagainst by a pressure roll 20a, whence it is removed by a diagonal doctor or knife 2!. The amount of stretchability which may be imparted to the web bv the closing up of the weave as illustrated in Figures 4 and 6, will of course be determined by the character of the weave of the cloth and its ability'to be gathered in this fashion. The production of creping crinkles as such occurs essentially only after the amount of stretchability imparted to the web exceeds the ability of the weave of the cloth to be closed up as indicated. The cloth has the ability to contract in both directions in the manner illustrated in Figure 6, though it is possible to contract it in but one direction by disposin the knife parallel to one of the sets of threads. Since the stretchability imparted to a web in the creping process is controllable in known ways, it will now be evident how the nature of my product may be varied as desired.

The practice of my invention as described results in the production of highly stretchable cloth which nevertheless is not greatly bulked in thickness. It may be joined with other substances, whether webs, or films of amorphous substances.

Further investigation has indicated that the effect herein described is not dependent upon the use of very small quantities of adhesive. The contraction of the cloth as described occurs during the creping operation, and dependsprimarily on two factors. The threads of the cloth must be bound to the creping cylinder-substantially only at those points or small areas wherethe threads cross other threads to the creping cylinder side of the fabric so that the remaining portions of the threads will be free to attain the greater sinuosity diagrammatically represented in Figure 6 independently of the adhesive. Also as set forth above, the threads must not bev locked together at the places where they cross each other so as to unify the fabric and make it act like a homogeneous felted web. These conditions can be met in various ways. It is pointed out that if the condition of the adhesive at the time ofapplication is such as to tend to be wholly absorbed into the fabric or the threads thereof, it will tend to strike through or around the threads and cement them together where they cross if its quantity is suflicient. For this reason, it is well to avoid the use of adhesives which are very highly fluid. Some absorption into or on the threads or fibers is not per se disadvantageous if the threads are left free of each other where they cross. In some adhesive applications it is easier to obtain the required association of the adhesive and the threads by using a viscous, non-penetrating adhesive and metering it to a very thin film on such an apparatus as is shown in Figure 2, thereupon pressing the cloth into contact with it and removing the cloth, the result being a discontinuous ;type of coating hereinabove referred to and illustrated in Figures}; and 5.

Even with a viscous coating, however, it is possible to fail to achieve the relationship of adhesive and fabric necessary to the practice of this invention. For example, if a relatively thick coating of adhesive is provided and the cloth is pressed into it to the extent that it contacts the threads substantially throughout their length, they will not only be bound together at or near their cross points, but they are also likely to be bound to the creping cylinder so nearly coextensively with their length that the fabric will acts as a homogeneous web and crepe by the formation of creping crinkles.

Nevertheless, the thickness of the adhesive per se is not the controlling factor since it is quite possible to attain the two important factors set forth above irrespective of the thickness of the adhesive. For example, if a thick coating of viscous adhesive is formed on a roll or surface and the cloth is led to that surface and pressed thereagainst so lightly that only the highest points of the threads on the side of the coating contact it, the desired conditions will be met and the cloth will be satisfactorily contracted in the creping operation, assuming that the layer of adhesive is itself displaceable by thickening or otherwise due to the action of the creping doctor. Under these circumstances the film of adhesive may be continuous, and need not be discontin uous. It will now be evident that when cloth is associated with adhesive in the way indicated, care must be taken that at any point where pressure is applied to the cloth, as in the relatively heavy pressure used in afiixing the cloth to the creping cylinder, such softening of the adhesive is avoided as would cause it to squeeze into the interstices of the cloth under the actual pressures used.

Since it is relatively difficult to associate a heavy continuous film with cloth in a coating apparatus such as that shown in Figure 2, and then remove the combination intact from the applicator roll I4, I prefer when contracting cloth with thick continuous films of adhesive to apply the adhesive uniformly to the first creping cylinder l8 and then lead untreated or previously treated cloth into contact with it, controlling the pressure exerted by the pressure roll l8a to bring about the condition above described.

As another example of a procedure in which the thickness or total weight of the adhesive associated with the cloth is not a limitation, I may point out that it is readily possible to coat the cloth with a light, discontinuous layer of adhesive after the manner described in connection with Figures 2, 3 and 5 and then re-coat it one or more times, the second or other applications of adhesive simply building up on the surfaces of the initial coated areas 5 and 6 in Figure 5. In this way also large quantities of adhesive may be associated with cloth which still is left in a condition to be contracted as described through the action of the creping surface and doctor.

I have described how the creping adhesive may act to retain the contracted condition of the cloth. This adhesive may be employed to adhere the contracted cloth to other webs, such for example as webs of universally expansible paper, which may be coated or uncoated. Or the contracted cloth may itself be recoated after creping. It helps to prevent loss of stretchability if the recoating substance is one not affecting the bond of the initial creping adhesive. Different adhesives may thus be used. Where contracting has been done with the aid of a thermosetting resin, this resin may be caused to set up by heat,

before recoating the web. Again, where the web.

has been contracted with the aid of rubberwhether derived from a dispersion or not-this rubber will not be affected by the application of additional rubber dispersion, e. g. rubber latex. But my contracted cloth may also be pressed onto a preformed rubber sheet.

A composite product comprising my contracted cloth in combination with a stretchable rubber layer offers unique advantages. Such a product combines stretchable rubber with stretchable cloth; but the cloth furnishes a textile reinforcement for the rubber at a time when. under stress, an amount of stretchability has been realized in the rubber equal to the stretch-- ability of the cloth. In a somewhat similar manner, a composite product of my cloth and a stretchable paper offers unique advantages. As shown in U. S. Patent No. 2,071,362 I have disclosed a bag formed of universally stretchable paper in which the ability of the structure to withstand shocks is. dependent not upon its ultimate bursting strength, but upon its ability to distort under shock. If my contracted cloth be combined in such an article with a paper layer or layers of equal or greater stretchability the same action is had; but at or prior to the removal of all of the stretchability from the paper under repeated shocks, the stretchability of the cloth will also have been removed; and at that point the ultimate bursting strength of the fabric of the bag becomes effectively very much greater. Morover, the cloth contributes to the paper layer or layers very much enhanced resistance to snagging. The fact that my cloth is contracted without any great bulking in thickness and without the production of large and irregular creping crinkles, makes these applications possible in many instances where ordinary creped cloth could not be used at all.

To illustrate such composite products, I have shown in Figure 7 my creped cloth 3, 4 joined top layer 22 which may be an amorphous film such as rubber, cellulosic derivatives, etc. or creped paper.

My invention also contemplates the production of a very considerable degree of universal stretchability in a woven cloth web by a procedure involving but one creping operation. This will be understood when it is remembered that by reason of its weave, cloth already has a fair degree of stretchability in the two bias directions. It is not appreciably stretchable in the directions of the warp and woof threads; but it is appreciably stretchable in directions substantially 45 to the major axes of the web and and to the threads.. If cloth be contracted in accordance with this invention in a single diagonal direction, as by being given the first creping operation described above, stretchability will be imparted to it in the directions of the warp and woof threads and of the axes of the web, 1. e., in those directions in which is has hitherto not been stretchable. Since it was already stretchable in other directions, it will now be found to be universally stretchable.

Again, tensioning cloth lengthwise tends to straighten the warp, and thereby contracts the woof, imparting to the cloth a considerable degree of widthwise stretchability. If cloth is first coated as I have described, and then strongly tensioned in applying it to a creping surface, I have found that it is possible to give it a considerable degree of universal stretchabilit by merely contracting it once by means of a creping doctor set normal to the direction of motion of the cloth.

Modifications may be made in my invention without departing from the spirit of it. Having thus described my invention, what I claim as new and desire to secure by Letters Patent is:

1. A cloth product characterized by a crowding together of at least one set of the threads therein, the opposite set of threads having an increased sinuosity whereby the product is rendered stretchable, the said increased sinuosity arising from the removal of said cloth from a creping surface by a doctor when the cloth is adhered to said surface by means of an adhesive so disposed as to bind to the creping surface essentially only the outermost portions of the threads of the cloth where they cross other threads. leaving them elsewhere unbound to the creping surface and to each other where they cross, the said cloth product bearing the said creping adhesive in the indicated association with the threads thereof, and being further characterized by substantial freedom from ordinary creping crinkles.

2. The product of claim 1 characterized by that crowding and increased sinuosity which is produced by a doctor continuously disposed slantwise to the direction of the threads in said cloth.

3. The product of claim 2 in which both sets of threads are crowded together and increased as to sinuosity by oppositely slantwise disposed doctors.

4. A contracted cloth of open weave characterized by a crowding together of at least one set 9 of the threads therein, the opposite set of threads being characterized by an increased sinuosity, in adherent union with at least one layer of creped paper having at least equal stretchability.

5. A contracted cloth product characterized by a crowding together of both sets of threads therein and increased sinuosity of both sets of threads. whereby the product is universally stretchable in combination with adhesive substance contacting the threads upon one side essentially only at the outermost portions of the threads on that side where they cross each other, the greater part of the several threads being out of contact with said adhesive and free of each other where they cross.

6. A process of contracting cloth which comprises cementing cloth to a creping surface by means of an adhesive acting to adhere the threads of the cloth to the surface essentially only at the outermost portions of said threads where they cross each other, leaving the threads elsewhere and in major portions of their length unbound to the creping surface and to each other where they cross, and removing said cloth from said creping surface by a creping doctor whereby to crowd together at least one set of threads in said cloth and produce an increased sinuosity of the opposite set of threads.

7. The process claimed in claim 6 wherein said cloth is tensioned longitudinally so as to contract it in width before it is cemented to said creping surface.

8. The process claimed in claim 6 wherein the said doctor is disposed slantwise to the sets of threads in said cloth.

9. The process claimed in claim 8 wherein the cloth is successively acted upon by doctors disposed oppositely slantwise to the threads of said cloth.

10. A process of contracting cloth which comprises associating cloth with a creping cylinder by means of a positive adhesive so related to the cloth as to contact only the outermost portions of the threads thereof where they cross each other, leaving the threads elsewhere and in major portions of their length unbound to the creping surface and to each other where they cross, and removing the cloth from said creping surface by means of a doctor whereby to crowd the threads of said cloth together and increase their sinuosity and whereby to displace the adhesive and concurrently contract it in area.

11. A process of contracting cloth which comprises applying to a creping cylinder a layer of adhesive substance of viscous character and bringing cloth into contact with said layer in such a way as to bind to the creping cylinder only the outermost portions of the threads of said cloth where they cross other threads therein, leaving the threads elsewhere and in major portions of their length unbound to the creping surface and to each other where they cross, and removing said layer and said cloth from said creping cylinder by means of a doctor whereby to contract said layer by displacement and to contract said cloth by crowding the threads thereof together and producing increased sinuosity in unbound portions of certain at least of said threads.

12. A process of producing a contracted cloth with which a moldable resin is associated, which consists in applying to cloth an application of an incompletely polymerized, thermo-setting synthetic resin of non-saturating viscosity, so as to produce a coated condition of only the highest parts of the threads upon one side of said cloth, the resin being located essentially in discontinuous areas on said highest parts, causing the cloth to adhere to a creping surface by means of said resin, removing said cloth from said surface by means of a doctor, whereby to produce a gathering in some at least of the threads of said cloth, and whereby certain at least of said resin areas are brought together in adhesive union to tend to cause a maintenance of the contracted condition of said cloth, causing a further polymerization of said resin whereby still to increase the bonds holding said cloth in contracted condition, and thereafter applying additional quantities of moldable resin to said web.

13. An expansible cloth product characterized by a crowding together of at least one set of the threads therein, the opposite set of threads having an increased sinuosity whereby the product is rendered stretchable, the said cloth product being further characterized by adhesive substance contacting the threads upon one side essentially only at the outermost portions of the threads on that side where they cross each other, the greater part of the several threads being out of contact with said adhesive and free of each other where they cross.

14. A process of producing a contracted cloth with which moldableresin is associated, which comprises associating cloth with a creping surface by means of an incompletely polymerized, thermosetting synthetic resin of non-saturating viscosity, so as to produce a coated condition of only the highest parts of the threads upon one side of said cloth, the-resin being located essentially in discontinuous areas of contact on said highest parts, removing said cloth from said surface by means of a doctor, whereby to produce a gathering in some at least of the threads of said cloth, and whereby certain at least of said resin areas are brought together in adhesive union to tend to cause a maintenance of the contracted condition of said cloth, and causing a further polymerization of said resin whereby still to increase the bonds holding said cloth in contracted condition.

WILLIAM WALLACE ROWE.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,944,001 Cluett Jan. 16, 1934 1,948,138 Sindler Feb. 20, 1934 2,008,182 Kemp July 16, 1935 2,061,748 Angier Nov. 24, 1936 2,079, 73 Angier May 4, 1937 2,291,258 Rowe July 28, 1942 

11. A PROCESS OF CONTRACTING CLOTH WHICH COMPRISES APPLYING TO A CREPING CYLINDER A LAYER OF ADHESIVE SUBSTANCE OF VISCOUS CHARACTER AND BRINGING CLOTH INTO CONTACT WITH SAID LAYER IN SUCH A WAY AS TO BIND TO THE CREEPING CYLINDER ONLY THE OUTERMOST PORTIONS OF THE THREADS OF SAID CLOTH WHERE THEY CORSS OTHER THREADS THEREIN, LEAVING THE THREADS ELSEWHERE AND IN MAJOR PORTIONS OF THEIR LENGTH UNBOUND TO THE CREPING SURFACE AND TO EACH OTHER WHERE THEY CROSS, AND REMOVING SAID LAYER AND SAID CLOTH FROM SAID CREPING CYLINDER BY MEANS OF A DOCTOR WHEREBY TO CONTRACT SAID LAYER BY DISPACEMENT AND TO CONTRACT SAID CLOTH BY CROWDING THE THREADS THEREOF TOGETHER AND PRODUCING INCREASED SINUOSITY IN UNBOUND PORTIONS OF CERTAIN AT LEAST OF SAID THREADS. 